Whitworth's resignation is effective on Wednesday. The technology products and services company said that its board will discuss appointing a new chairman at its next meeting.

Whitworth became HP's interim chairman in April 2013 after former chairman Ray Lane stepped down from his post. At the time that Lane stepped down, HP also announced that directors John Hammergren and G. Kennedy Thompson were leaving the board. The shake-up was spurred by disgruntled stockholders unhappy with HP's performance.

HP has been working on a turnaround of its business amid slumping PC sales in recent years, cutting expenses and focusing on more profitable areas such as software and services. Like other PC makers, the company had trouble keeping up with the likes of Apple and Samsung. Whitman has warned that the turnaround will be a long-term endeavour. The company's most recent earnings report, in February, topped Wall Street's expectations.

Whitworth, an activist shareholder, has served as an HP board member since 2011. The co-founder of Relational Investors LLC, he was named to the company's board to placate investors rattled amid management turmoil at the company following CEO Mark Hurd's ouster in 2010 amid an ethical scandal. Hurd's successor, Leo Apotheker, was ousted in September 2011 and replaced by former eBay CEO Meg Whitman, who is still at the company's helm.

"HP's shareholders can be very confident that Meg, her team and the current board will stick to the strong practices and discipline we've put in place," Whitworth said in a statement. "While I'm disappointed to step down from HP's board at such an exciting time for the company, it gives me great comfort that HP is in such talented and steady hands."

Whitworth is also taking a leave of absence from the privately held investment company he co-founded, Relational Investors. He was 58 as of a February regulatory filing, the latest available. HP could not immediately be reached Tuesday morning to confirm his age.

Shares of Palo Alto, California-based Hewlett-Packard Co. climbed 26 cents to $34.41 in morning trading on Tuesday. Its shares are up 23 per cent in 2014.